A depolarization and attenuation experiment using the COMSTAR and CTS satellites

Monthly statistical data are presented on ground rainfall rate and attenuation of satellite downlinks at 11.7 GHz, 19.04 GHz, and 28.56 GHz and on cross-polarization isolation at 11.7 GHz. Regression equations for relating isolation to attenuation, attenuation to rain rate, and attenuation at one frequency to attenuation at another frequency are also included. Longer-term statistics are also presented and discussed

Contextual Discrimination After Nonreinforced Preexposure to the Context

Rats were trained on a contextual discrimination after nonreinforcedpreexposure to both contexts. In Experiment 1, where contexts differed in terms oftactile and visual stimuli, preexposure retarded subsequent discrimination bycomparison with non preexposed controls (latent inhibition). In Experiment 2, wherecontexts differed only in terms of visual cue, discrimination was facilitated inpreexposed animals (perceptual learning). Food was used as reinforcer and anticipatoryactivity as dependent measure. These results suggest that contextual similarityinfluences the outcome of nonreinforced preexposure

Co-registration of cortical magnetic stimulation and functional magnetic resonance imaging

FUNCTIONAL magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) are noninvasive techniques recently used to investigate cortical motor physiology. However, these modalities measure different phenomena, and in studies of human motor control they have given inconsistent results. We have developed a reproducible technique which co-registers TMS and fMRI, using a frameless method. In four normal subjects, the TMS map and fMRI activation were present on the primary motor cortex contralateral to the target hand, with some extension into primary sensory cortex. fMRI activation alone was also present in the medial motor cortex bilaterally and in the sensori-motor cortex ipsilateral to the target hand. This technique allows a more comprehensive evaluation of the physiologic events involved in motor control